Abstract
Visually induced illusory self-motion (vection) is generally facilitated by consistent information of self-motion from other modalities. We provide three examples that consistent information between vision and other proprioception enhances vection, ie, locomotion, air flow, and sounds. We used an optic flow of expansion or contraction created by positioning 16,000 dots at random inside a simulated cube (length 20 m), and moving the observer's viewpoint to simulate forward or backward self-motion of 16 m/s. First, We measured the strength of forward or backward vection with or without forward locomotion on a treadmill (2 km/h). The results revealed that forward vection was facilitated by the consistent locomotion whereas vections in the other directions were inhibited by the inconsistent locomotion. Second, we found that forward vection intensity increased when the air flow to subjects' faces produced by an electric fan (the wind speed was 6.37 m/s) was provided. On the contrary, the air flow did not enhance backward vection. Finally, we demonstrated that sounds which increased in loudness facilitated forward vection and the sounds which ascended (descended) in pitch facilitated upward (downward) vection.